HN guidelines strongly encourage me not calling you an asinine twat, so I won't do that. As your other reply highlighted, no one's arguing thermodynamics with you. It's clearly a behavioural phenomenon, and one that isn't half as well understood as we may like to believe. It's at the intersection of advertising, biology, dietetics, economics, genetics, neuroscience, nutrition, psychiatry, psychology, sociology, the disciplines go on. Consider all the myriad ways those factors may interact and compound, then look at the statistics: that the overwhelming majority of adults fail to lose significant weight long term through "eat less" should tell you all you need to know about the state of the problem. If your conclusion is as simple as "they mustn't have considered to put the fork down and try harder, en masse," I feel it says more about you than anything else.